Exemplary embodiments of the present disclosure relate to a yaw brake system, and more particularly, to a yaw brake system capable of preparing for buildup of equipment, such as a blade, a hub, or a nacelle, depending on an increase in power of wind power generation, and at the same time capable of more effectively braking yawing of the nacelle due to a rapid change in wind direction.
A wind generator like a wind turbine is an environmentally-friendly power plant that converts rotational energy generated by wind into electric energy and is a part of new renewable energy businesses that have been spotlighted recently as the need to protect the earth's environment is getting more important.
Such wind generator may be classified into a nacelle and a tower. The nacelle includes a plurality of blades, a hub, a rotor, a generator, a variety of sensors, a yaw brake, etc.
The blades are integrally coupled at predetermined intervals in a circumferential direction about the hub. The center of the hub is connected to a drive shaft of the rotor, and the drive shaft is connected to the generator.
When the blades are rotated by wind, the hub mounted with the blades rotates together, and the drive shaft of the rotor thus rotates to drive the generator. As a result, rotational energy by wind is converted into electric energy. This electric energy is transferred to a power system via the interior of the tower through power cables connected to the generator.
Meanwhile, the wind generator is designed to always generate maximum power in such a manner that the nacelle rotates corresponding to a change in wind direction during “yawing”. This system is referred to as a “yaw system”.
Referring to FIG. 1, a yaw system may include a yaw bearing 3 having a rack gear 3a, which is circumferentially disposed in the upper portion of a tower 2, yaw drives 4 mounted in the lower portion of a nacelle 1, each having a pinion gear 4a which is formed at the lower end thereof and engages with the rack gear 3a, and the like.
When the wind direction is changed, the yaw drives 4 yaw along the yaw bearing 3 in order to move a plurality of blades in a windward direction.
However, when the nacelle 1 yaws, in particular when the wind direction is rapidly changed, a very large yaw moment occurs, and a yaw brake 5 is required to brake this yaw moment.
The yaw brake 5 may include a yaw disk 6, a plurality of yaw brake blocks 8, a plurality of friction pads 7, etc. First, the yaw disk 6 has an annular shape and is circumferentially disposed in the upper portion of the tower 2. The yaw brake blocks 8 are arranged in the lower portion of the nacelle 1. In this case, the yaw brake blocks 8 and the yaw drives 4 may be arranged alternately at regular intervals in order to reduce spatial interference therebetween.
The friction pads 7 are mounted on each of the yaw brake blocks 8. The friction pads 7 strongly press the yaw disk 6 by hydraulic pressure supplied thereto, and thus brake yawing.
In this case, the friction pads 7 are always in contact with the yaw disk 6, unlike the case of typical braking, thereby restricting a yaw moment value varying according to the yawing of the nacelle 1. When the excessive yawing of the nacelle 1 occurs due to a rapid change in wind direction, the friction pads 7 more strongly press against the yaw disk 6 by hydraulic pressure additionally supplied thereto, and thus brake extreme yawing.
In recent years, wind generator has gradually become larger due to an increasing need for wind power generation and an increase in power, and the sizes of the blades and the nacelle 1 thus tend to increase.
Accordingly, a larger braking force is desirable to control yawing since a yaw moment value is increased along with the yawing of the nacelle 1 as the weight of the nacelle 1 is increased. However, the yaw brake 5 has a limit in coping with such variation, and it is difficult to constitute a separate brake in the nacelle 1 due to a limited space therein.